The energy efficiency of portable computer devices has long been a focus of development.
Although battery operation has continuously improved, there is still a need for alternative sources of energy to supplement battery power. Solar energy devices have been employed in a variety of ways to prolong the available period of battery operation. One typical approach is shown in U.S. Pat. No. 5,260,885 in which extendable solar panels are provided to collect ambient radiant energy. This energy provides a supplemental source of electric power to assist in battery operation.
Japanese Patent No. 4-362917 describes an LCD display in which the solar panel is mounted behind the display to collect ambient light transmitted through the display. Although this configuration eliminates the need for cumbersome fold out panels, it does so in a manner which reduces the performance of the display. The LCD display is generally unsuitable for this application because of the inherent nature of the cells that create the image of the display. These cells or pixels alternate between visible and non-visible states depending on the excitation generated by the display in response to instructions from the computer. In the LCD display the light passes through the visible cell and is reflected by a reflective layer behind the cell or it is generated by a lamp behind the cell. The cell, therefore, must be transparent in order to be visible. The cells of an LCD display, therefore, alternate between light absorbing and light transmitting states. Since the performance of the solar panel also relies on transmitted light, it necessarily competes with the reflected light required for image definition on the display. This will erode the performance of the display.
It is the purpose of this invention to construct a display which allows the use of transmitted light to excite a photovoltaic cell and generate supplemental energy to improve battery operation without affecting the image definition capability of the: display. It is also the purpose of this invention to excite the photovoltaic cell during operation of the computer or other device.